Sheet reading apparatus for detecting the shadow of a conveyed sheet to determine an inclination

Abstract

A sheet reading apparatus includes a sheet table on which a sheet is placed, a conveyor configured to convey the sheet, a reading guide configured to guide the sheet conveyed by the conveyor, and a reading device configured to read a shadow of the sheet conveyed by the conveyor, for detection of an inclination of the sheet. The sheet reading apparatus further includes a transparent member disposed at a position on a reading line of the reading device. The position on the reading line is withdrawn from the sheet and adjacent to the reading guide.

What is claimed is: 
     
       1. A sheet reading apparatus comprising:
 a sheet table on which a sheet is placed; 
 a conveyor configured to convey the sheet; 
 a reading guide configured to guide the sheet conveyed by the conveyor, the reading guide including a guide face; 
 a reading device including a scanner configured to read, through a reading table which is parallel to the guide face, a shadow of the sheet conveyed by the conveyor, for detection of an inclination of the sheet; 
 a transparent element disposed at a position on a reading line of the reading device, the position on the reading line being withdrawn from the sheet and adjacent to the reading guide, the transparent element having a non-changeable surface at a side of the transparent element opposite to the reading table such that light passing through the transparent element is not reflected off of any changeable surface at the side of the transparent element opposite to the reading table; and 
 a recess which is recessed from the guide face and which is further from the reading table than the guide face. 
 
     
     
       2. The sheet reading apparatus according to  claim 1 , wherein:
 the non-changeable surface includes a white sheet disposed between the transparent element and the reading guide. 
 
     
     
       3. The sheet reading apparatus according to  claim 1 ,
 wherein the reading guide including the recess is made of metal. 
 
     
     
       4. The sheet reading apparatus according to  claim 1 , further comprising:
 a sheet detector configured to detect presence or absence of the sheet on the sheet table; 
 a sheet nip assembly configured to nip the sheet on the sheet table; and 
 a driver configured to apply a conveyance force to the sheet nip assembly nipping the sheet, to convey the sheet toward the conveyor. 
 
     
     
       5. The sheet reading apparatus according to  claim 1 , further comprising:
 a skew amount detector configured to detect, based on the shadow of the sheet projected on the reading guide, a skew amount of an image of the sheet read by the reading device; and 
 circuitry configured to correct an inclination of the image read by the reading device based on the skew amount. 
 
     
     
       6. The sheet reading apparatus according to  claim 1 , wherein the sheet is a document sheet. 
     
     
       7. An image forming apparatus comprising:
 the sheet reading apparatus according to  claim 1 ; and 
 an image forming device configured to form an image.